Process automation field devices are discrete devices used in a process automation system for the measurement of some physical phenomena or for the control of some device such as a valve, pump, switch, etc. In a typical embodiment of a field device, the field device includes electronics such as a microcontroller, memory, transducers, and analog-to-digital converters. The field device may include digital and analog outputs, and the field device may include a user interface such as a display screen. A field device will include a housing that encloses and protects the components of the field device.
A process automation field device usually includes a communication interface for communicating with the central controller of the process automation system. This communication interface may be a wired interface such a 4-20 mA current loop, a HART network, or a digital field bus, or the communication interface may be a wireless interface such as WiFi or wireless HART
There is often a need for point-to-point communication with a field device. For example, a technician servicing or calibrating a field device may need access to the field device directly for reading, modifying, and writing the field device's internal parameters. For point-to-point communication, access of the field device via the process automation control network (e.g., 4-20 mA, FieldBus, HART, etc.) may not be practical or possible. Therefore a process automation field device may include an additional communication interface such as a wired serial interface or a wireless interface such as a Bluetooth Low Energy interface for point-to-point communication.
However, constraints on the design of the field device may make the inclusion of these point-to-point communication interfaces impractical. For example, safety design constraints may prevent the inclusion of electrical contacts for a wired serial interface, or a metal field device housing may interfere with the operation of wireless communications antennae. In addition, the power requirements for a field device may prevent the inclusion of a point-to-point communication interface; there may not be sufficient power available to the field device to operate the point-to-point communication means in addition to the field device's normal functions.
Accordingly, there remains a need for further contributions in this area of technology.